Comparison of the 7th and 8th Editions of the AJCC/UICC Staging for Human Papillomavirus–Related Oropharynx Carcinoma

Abstract

The current 7th edition AJCC/UICC staging system for oropharyngeal cancer fails to adequately reflect outcomes for human papillomavirus–associated oropharynx cancer given the more favorable prognosis compared to non-HPV–related oropharynx cancer. The upcoming 8th edition AJCC/UICC staging system incorporated concepts developed from the ICON-S classification system for HPV-related oropharynx cancer. The purpose of this study is to compare the validity between the 7th edition and upcoming 8th edition clinical staging systems in a large prospectively collected single-institution cohort. Data from 486 patients treated for HPV-related oropharyngeal cancer with definitive intent at a single academic cancer center were analyzed. Disease, demographic, smoking, and treatment data were collected prospectively. Patients were initially classified according to AJCC 7th edition and retrospectively restaged according the upcoming 8th edition clinical staging systems. Kaplan-Meier was used to compare rates of overall survival. Multivariate Cox regression was used to correlate stage, age, and smoking status with overall survival. Utilizing the 7th edition staging system, 422/486 (87%) patients were classified as stage IV; 47/486 (9.6%) were stage III; 12/486 (2.5%) were stage II; 5/486 (1%) were stage I. Utilizing the 8th edition clinical staging system, 137/486 (28.2%) were stage III; 98/486 (20%) were stage II; 250 (51.4%) were stage I. Fifty percent (211/422) of the 7th edition stage IV patients were reclassified as a stage I in the 8th edition; 17% (73/422) were reclassified as a stage II; and 33% (138/422) were reclassified as a stage III in the 8th edition system. There was no significant difference in the survival curves of stage III and stage IV in the 7th edition, and there were too few of stage I/II to analyze in the 7th edition. The 8th edition clinical staging demonstrated statistically significant differences in survival curves across each stage (P<.0001). The 2-year and 5-year overall survival was 95%/90% for stage I; 93%/79% for stage II; and 86%/61% for stage III. In multivariable analysis, controlling for age and 8th edition staging, smoking was significantly associated with OS (P=.03). Conclusion: This analysis is the largest series to date to validate the findings of the ICON-S staging system and apply the 8th edition AJCC/IUCC clinical staging system in a large single-institution cohort. Clinical restaging of the cohort from the 7th edition to the 8th edition provides an improved balance between stages and provides prognostic information that is missing from the 7th edition system. Author Disclosure: K. Casper: None. P.G. Hawkins: None. M. Mierzwa: None. E. Bellile: None. K. Malloy: None. S.B. Chinn: None. M.E. Spector: None. A. Shuman: None. C.L. Stucken: None. S. Mclean: None. F. Worden: Research Grant; Bristol Myers Squibb. Honoraria; Bristol Myers Squibb, Merck. Advisory Board; Bristol Myers Squibb, Genzyme, Merck. P.L. Swiecicki: None. J. Taylor: None. C.R. Bradford: None. M.E. Prince: None. G.T. Wolf: Research Grant; IRX Therapeutics, Inc. Consultant; IRX Therapeutics, Inc. Advisory Board; IRX Therapeutics, Inc. A. Eisbruch: None.